The manufacture of plastic pipes from thermosetting plastic which may contain a filler, namely a polyester or epoxy resin mixed with calcium carbonate, for example, sand and glass fibres in a rotating, horizontally-axised metallic centrifugal drum serving as a mould, is known of per se. In installations of this type, the starting materials are distributed evenly from an arm moving to and fro in the centrifugal drum, and the composition of the wall of the pipe is formed according to the purpose for which it is intended, and in accordance with the dimensions it should have. Although the thermosetting reaction is an exothermic process, to ensure that the process runs correctly and predictably it is not only practical, but necessary, to supply heat after the first introduction of starting materials at room temperature into the centrifugal drum, which is also at room temperature. This is currently done by blowing hot air into the centrifugal drum. The air which is thereby blown out of the centrifugal drum carries gaseous solvents from the liquid resin or the catalyst, so that in accordance with new environmental findings and regulations, purification installations are required for this exhaust air.